Rausch will re-join TT as executive vice president of global support and chief information officer in January. He left TT in June as executive vice president of global support and services, to become Calyon Financial's head of e-brokerage sales for North America.

He will oversee TT's technology and information infrastructures and manage customer support efforts. He will be based in Chicago and report to Harris Brumfield, chief executive officer.

Calyon Financial spokesman said Rausch was hired in June as the firm entered into a software license agreement with TT. He said Rausch was instrumental in helping the firm integrate TT software into its overall electronic trading offerings during the past several months.

Both firms declined to comment further on Rausch's departure from Calyon Financial.

TT has been involved in legal battles with several derivatives exchanges, brokers and rival vendors this year, alleging they used trading systems for their clients that infringed on a patent TT secured last year. It has since settled charges with a number of firms, including this month's settlement London-based alternative investment firm Man Group.